Beginning in 1996, the WHI Memory Study (WHIMS) enrolled participants from the WHI hormone trials to test whether hormone therapy prevented cognitive decline, mild cognitive impairment, and probable dementia (including Alzheimer's disease). After the WHI hormone trials were stopped early, previous industry funding was withdrawn. NHLBI agreed to 4 years of funding to complete the Estrogen-Alone trial;continue monitoring post-trial cognitive health;and perform brain MRI scans to elucidate the role of vascular disease. Given the findings to date, the increasing population dementia burden, and the need to study its causes using both classic epidemiologic methods and new technologies, NHLBI extended this project in 2008 in order to fully leverage this unique resource.